Organic depth profiling of C₆₀ and C₆₀/phthalocyanine layers using argon clusters

Abstract

Molecular semiconductor devices, such as light-emitting diodes and photovoltaic cells, have recently received considerable attention because of their compatibility with flexible substrates and large-area applications. Because of the importance of the interfacial properties for the performance of the devices, these organic (multi)layers constitute an important field of application for molecular depth profiling by SIMS. In this contribution, we investigate the use of C 60 n+ and Ar 1000-2000 + cluster projectiles at different energies (ranging from 2.5 to 20 keV) as sputter ions for the organic depth profiling of fullerene-based films and heterojunctions. The bilayers consist of C 60 fullerenes on tin phthalocyanine (SnPc), deposited on silicon substrates. Our preliminary results showed that C 60 films could not be successfully profiled using C 60 n+ ions in regular analysis conditions (room temperature). In contrast, with Ar clusters, the depth profiling is successful (except for 20 keV Ar 1000 ) and the sputtered volume shows a linear relationship with the Ar cluster energy. Surprisingly, for a given total energy of the projectiles, Ar 2000 sputters approximately two times more than Ar 1000 . The observations are tentatively explained as being the result of a balance between the sputtering and the cross-linking efficiency for the different bombardment conditions, larger clusters being expected to naturally induce less cross-linking than smaller clusters with the same total energy.

Re-print of “Sputtering of polymers by keV clusters: Microscopic views of the molecular dynamics”

“…These simulations nicely explain the different behavior of C 60 and Ar n cluster for the depth-profiling of polystyrene [70] and materials involving fullerene molecules [57,71]. Moreover, they indicate that the crosslinking caused by Ar n clusters could become problematic as the energy/amu in the projectile increases, an effect also observed in the experiments [57,71].…”

Surface sputtering with nanoclusters: the relevant parameters

“…These preliminary results need to be completed for a wider range of projectiles and organic materials, such as polystyrene, but they are in broad agreement with our measurements performed on fullerene and PCBM : P3HT photovoltaic layers. [30] Conclusion A variety of clusters, atomic and molecular, are used for molecular surface analysis and depth profiling of carbon-based inorganic and organic materials. The simulation results gathered here show that the sputtering yields, the molecular fragmentation, and the induced crosslinking generally depend on the total energy and the energy per atom/per nucleon in the projectile, a quadratic function of the velocity, whereas the range evolves linearly with the velocity for cluster atomic masses equal or larger than that of the target.…”

GD-OES and XPS coupling: A new way for the chemical profiling of photovoltaic absorbers

“…Concerning organic layers, ToF-SIMS [9] and more recently GD-TOFMS [10] have been successfully used. In the case of ToF-SIMS, the development of new ion beams is offering a better characterization of the highly breakable organic layers [9].…”

“…Thin films and interfaces in microelectronics are often conducted with XPS assisted by vibrational techniques to obtain composition and chemistry as a function of depth [8]. Concerning organic layers, ToF-SIMS [9] and more recently GD-TOFMS [10] have been successfully used. In the case of ToF-SIMS, the development of new ion beams is offering a better characterization of the highly breakable organic layers [9].…”